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// Copyright 2020 The gVisor Authors.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// +build go1.13
// +build !go1.17
// Check function signatures and constants when updating Go version.
package sync
import (
// Note that go:linkname silently doesn't work if the local name is exported,
// necessitating an indirection for exported functions.
// Memmove is runtime.memmove, exported for SeqAtomicLoad/SeqAtomicTryLoad<T>.
func Memmove(to, from unsafe.Pointer, n uintptr) {
memmove(to, from, n)
//go:linkname memmove runtime.memmove
func memmove(to, from unsafe.Pointer, n uintptr)
// Gopark is runtime.gopark. Gopark calls unlockf(pointer to runtime.g, lock);
// if unlockf returns true, Gopark blocks until Goready(pointer to runtime.g)
// is called. unlockf and its callees must be nosplit and norace, since stack
// splitting and race context are not available where it is called.
func Gopark(unlockf func(uintptr, unsafe.Pointer) bool, lock unsafe.Pointer, reason uint8, traceEv byte, traceskip int) {
gopark(unlockf, lock, reason, traceEv, traceskip)
//go:linkname gopark runtime.gopark
func gopark(unlockf func(uintptr, unsafe.Pointer) bool, lock unsafe.Pointer, reason uint8, traceEv byte, traceskip int)
// Goready is runtime.goready.
func Goready(gp uintptr, traceskip int) {
goready(gp, traceskip)
//go:linkname goready runtime.goready
func goready(gp uintptr, traceskip int)
// Values for the reason argument to gopark, from Go's src/runtime/runtime2.go.
const (
WaitReasonSelect uint8 = 9
// Values for the traceEv argument to gopark, from Go's src/runtime/trace.go.
const (
TraceEvGoBlockSelect byte = 24
// Rand32 returns a non-cryptographically-secure random uint32.
func Rand32() uint32 {
return fastrand()
// Rand64 returns a non-cryptographically-secure random uint64.
func Rand64() uint64 {
return uint64(fastrand())<<32 | uint64(fastrand())
//go:linkname fastrand runtime.fastrand
func fastrand() uint32
// RandUintptr returns a non-cryptographically-secure random uintptr.
func RandUintptr() uintptr {
if unsafe.Sizeof(uintptr(0)) == 4 {
return uintptr(Rand32())
return uintptr(Rand64())
// MapKeyHasher returns a hash function for pointers of m's key type.
// Preconditions: m must be a map.
func MapKeyHasher(m interface{}) func(unsafe.Pointer, uintptr) uintptr {
if rtyp := reflect.TypeOf(m); rtyp.Kind() != reflect.Map {
panic(fmt.Sprintf("sync.MapKeyHasher: m is %v, not map", rtyp))
mtyp := *(**maptype)(unsafe.Pointer(&m))
return mtyp.hasher
type maptype struct {
size uintptr
ptrdata uintptr
hash uint32
tflag uint8
align uint8
fieldAlign uint8
kind uint8
equal func(unsafe.Pointer, unsafe.Pointer) bool
gcdata *byte
str int32
ptrToThis int32
key unsafe.Pointer
elem unsafe.Pointer
bucket unsafe.Pointer
hasher func(unsafe.Pointer, uintptr) uintptr
// more fields
// These functions are only used within the sync package.
//go:linkname semacquire sync.runtime_Semacquire
func semacquire(s *uint32)
//go:linkname semrelease sync.runtime_Semrelease
func semrelease(s *uint32, handoff bool, skipframes int)
//go:linkname canSpin sync.runtime_canSpin
func canSpin(i int) bool
//go:linkname doSpin sync.runtime_doSpin
func doSpin()